Touch screens are commonly used as input devices for a variety of electronic products and for a variety of different applications. Touch screens are known to allow a user to interact with an electronic product in more intuitive and versatile manner as compared to other known input devices. Touch screens can be used for example to select virtual buttons displayed on the screen, to manipulate size and position of displayed objects, to enter data with a virtual keyboard, virtual number pad and/or by handwritten input, to open a document or application, to scroll within a window, to draw and/or to play games.
Some touch screens additionally or alternatively support stylus detection. Styluses may be particularly useful for applications that require touch detection with higher resolution such as drawing applications and/or applications that require handwritten input. Some applications are specifically geared toward receiving input from a stylus such as for example security applications that require a user to provide a handwritten signature. At times, usage of a stylus is a personal preference. Known styluses include passive styluses that may be powered by the electronic device and/or active styluses that may be battery powered.
Touch screens are often used for operating portable devices, such as Personal Digital Assistants (PDA), tablet PCs, wireless flat panel displays (FPD) screens, laptop computers, smart phones and other devices. Since these portable devices are typically battery-powered, power management techniques are typically employed to prolong the battery life of these devices. Known power management techniques include for example screen blanking while the screen is not being used and/or hibernating one or more input/output devices while they are not being used.
U.S. Pat. No. 7,843,439 entitled “Touch Detection for a Digitizer” assigned to N-Trig Ltd., the contents of which is incorporated herein by reference, describes a detector for detecting both a stylus and touches by fingers or like body parts on a digitizer sensor. The detector typically includes a digitizer sensor with a grid of sensing conductive lines, a source of oscillating electrical energy at a predetermined frequency, and detection circuitry for detecting a capacitive influence on the sensing conductive line when the oscillating electrical energy is applied, the capacitive influence being interpreted as a touch. The detector is capable of simultaneously detecting multiple finger touches and/or stylus touch.
U.S. Pat. No. 8,289,289 entitled “Multi-Touch and Single Touch Detection” the contents of which is incorporated herein by reference, describes a touch detection system and method for selectively applying a first touch detection method over a first selected part of a touch sensitive sensor and a second touch detection method over a second selected part of the same touch sensitive sensor. It is described that positions and sizes of the first and second selected parts of the touch sensitive sensor can be set in accordance with an application being used or dynamically defined or changed during operation of the application.
U.S. Pat. No. 5,396,635 entitled “Power conservation apparatus having multiple power reduction levels dependent upon the activity of the computer system” the contents of which is incorporated herein by reference, describes a method and apparatus for power management in a computer. A power conservation system of the computer has a plurality of states of operation including an ON state, a DOZE state, a SLEEP state and an OFF state. An activity monitor monitors the activity of the computer system and generates control signals for selecting one of the states of operation for the computer system. During periods of inactivity, power consumption is reduced, for example, by reducing clock speeds or removing clocks, and/or by removing power, and/or by controlling the refresh frequency to memory.